Water-soluble polyesters from long chain alkylesters of citric acid and poly(ethylene glycol)

Abstract

Long chain aliphatic alcohols have been used as model compounds to develop a preparative method for a water-soluble material, which could be a carrier for triacontanol, a highly hydrophobic plant growth regulator. New polyesters from long chain aliphatic (C = 12, 18 and 22) mono-1-alkyl citrates and poly(ethylene glycol) were synthesized and characterized by NMR spectroscopy. The polyester containing the triacontyl moiety was obtained from mono-1-triacontyl citrate, which was synthesized from the corresponding alcohol extracted from the Agave fourcroydes. The molecular weight Mn of the polyesters depends on experimental conditions during synthesis such as reaction time, atmosphere, catalyst concentration and temperature. The reaction is second order in the early stage of the polyester synthesis. The reaction rate constant is independent of the length of the aliphatic chain, but it decreases with increasing Mn of the poly(ethylene glycol) employed. Turbidity measurements have been used to study the polyester solubility. Solubility characteristics were found to depend on the Mn of poly(ethylene glycol), the aliphatic-chain length and the value of Xn for the polyester. These preparations could potentially be used to release triacontanol.